The present invention relates generally to surgical procedures for spinal stabilization and more specifically to instrumentation adapted for inserting a spinal implant within the intervertebral disc space between adjacent vertebra. More particularly, while aspects of the invention may have other applications, the present invention is especially suited for disc space preparation and implant insertion into a disc space from a generally anterior approach to the spine.
Various surgical methods have been devised for the implantation of fusion devices into the disc space. Both anterior and posterior surgical approaches have been used for interbody fusions. In 1956, Ralph Cloward developed a method and instrumentation for anterior spinal interbody fusion of the cervical spine. Cloward surgically removed the disc material and placed a tubular drill guide with a large foot plate and prongs over an alignment rod and then embedded the prongs into adjacent vertebrae. The drill guide served to maintain the alignment of the vertebrae and facilitated the reaming out of bone material adjacent the disc space. The reaming process created a bore to accommodate a bone dowel implant. The drill guide was thereafter removed following the reaming process to allow for the passage of the bone dowel which had an outer diameter significantly larger than the reamed bore and the inner diameter of
More recent techniques have advanced this concept and have provided further protection for sensitive tissue during disc space preparation and dowel insertion. Such techniques have been applied to an anterior approach to the lumbar spine. In one approach, a unilateral template has been provided to evaluate the space in the disc space. For bilateral implant placement, the template entire device must be rotated and visually aligned to approximately 180xc2x0 from the previous position. Thus, there is the chance for operator error in rotating the device to the correct position. Further, there is little guidance to ensure proper alignment of cutting instruments extending through the template.
One approach to provide such alignment is the use of a guide wire extending through a cannulated cutting instrument, such as a trephine. However, for instruments with hollow cutting heads, there is typically no engagement between the inner walls of the hollow cutting head and the guide wire. Thus, the guide wire may bend between the portion extending into the tissue and the guide wire entrance into the cannula of the instrument. As a result, the hollow cutting head may not remain in substantial alignment with the guide wire, resulting in improper opening formation. Therefore, there remains a need for improved guiding mechanisms for cutting instruments.
Once an initial opening or openings have been made in the disc space, the height of the disc space is normally distracted to approximate the normal height. Typically, a first distractor with a height estimated by CT or MRI examination is inserted. If additional distraction is required, the first distractor is removed and a second, larger distractor is inserted. However, since the positioning of the distractors is usually performed without the benefit of protective guide sleeves, the switching of distractors increases the potential for damage to neurovascular structures and may increase the time of the procedure.
For bilateral procedures, a double barrel sleeve may be inserted over a pair of previously placed distractors with a central extension extending into the disc space to maintain distraction. One limitation on guide sleeve placement is the amount of neurovascular retraction that must be achieved to place the guide sleeves against the disc space. For some patients, a double barrel sleeve may not be used because there is insufficient space to accept the sleeve assembly. Further, although the distal end of the sleeve assembly may be configured to engage the vertebral surface, if material has been removed from the disc space, there is the potential that adjacent neurovascular structures may encroach on the working channels in the disc space, resulting in damage to these structures caused by contact with instruments. While visualization windows on the guide sleeve may assist in better visualization of procedure steps and verifying unobstructed working channels prior to tool insertion, the windows themselves may allow tissue to come into contact with instruments in the working channels. Thus, there remains a need for guide sleeves requiring reduced neurovascular retraction for proper placement and providing greater protection to adjacent tissue.
While the above-described techniques are advances, improvement is still needed in the instruments and methods. The present invention is directed to this need and provides more effective methods and instrumentation for achieving the same.
The present invention relates to methods and instrumentation for vertebral interbody fusion. The present invention provides a guide sleeve having first and second working channels. The guide sleeve is removably engageable to a guide sleeve housing positioned in an operative location with respect to the disc space. The guide sleeve can be removed to enhance surgeon visualization while the guide sleeve housing maintains disc space distraction.
Sleeve assemblies according to the present invention can be provided with a reduced width portion adjacent the distal end to limit the amount of retraction of the surrounding vascular and neural structures required for the procedure. According to one aspect of the invention, a sleeve assembly is provided that includes a central distraction flange having a first height and an opposing pair of lateral flanges having a second height, less than the first height. The lateral flanges provide protection from encroachment of tissue into the working area in the disc space. The lateral flanges are provided on a guide sleeve housing removably mounted on the distal end of a guide sleeve. The central distraction flange can be provided as part of the guide sleeve housing or as part of the guide sleeve. It is further contemplated that neither the guide sleeve nor the guide sleeve housing is provided with a central distraction flange. With the guide sleeve removed from the guide sleeve housing, visualization by the surgeon of the working space in the disc space is enhanced.
In another aspect, the guide sleeve has first and second working channels and is removably attached to a guide sleeve housing at its distal end. The first and second working channels can be isolated by a central wall or are in communication with another to provide a reduced profile configuration.
In a further aspect of the invention, a guide sleeve housing is removably mounted to a housing inserter. The guide sleeve housing and housing inserter are movably mounted along a central distractor positioned in a spinal disc space. The guide sleeve housing is advanced along the distractor to insert at least lateral flanges of the guide sleeve housing into the disc space. The housing inserter is then uncoupled from the guide sleeve housing and removed. The central distractor is then removed with the guide sleeve housing remaining in the disc space. A guide sleeve can then be mounted to the guide sleeve housing and surgical procedures performed in the disc space through the guide sleeve and the guide sleeve housing. The guide sleeve is removable from the guide sleeve housing to enhance surgeon visualization of the operative site in the disc space. In one form, the central distractor is rotatable from a reduced height insertion and removal configuration to an increased height distraction configuration.
Related aspects, embodiments, forms, features, objects and advantages of the present invention will be apparent from the following brief description of the drawings.